NPY and early-onset autosomal dominant Alzheimer disease: Interestingly, NPY-ir cortical neurons are one of the first affected neuron populations in Alzheimer's disease, suggesting a unique vulnerability among interneurons that are known to be rather resistant to the disease (Beal et al., 1986b; Kowall and Beal, 1988; Hof and Morrison, 1991; Hof et al., 1991, 1993).